Field of the Invention
The present invention relates to electronics and, more specifically but not exclusively, to architectures for monitoring power or other characteristics in electronic systems.
Description of the Related Art
This section introduces aspects that may help facilitate a better understanding of the invention. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.
Electronic systems, such as printed circuit boards (PCBs), need power. The components in an electronic system can have multiple, different operating voltages. Furthermore, the power-up and/or power-down sequences can be important to avoid component damage when turning on and off electronic systems. Because of these issues, many electronic systems of even modest complexity are not instant on; instead, power is sequenced and controlled by a power management subsystem. Typically, the boards use thermal management ICs to monitor operating temperature of large devices on the board and control temperature using chip-mounted fans. In addition, digital components may also have digital control functions such as reset functions, system interfaces, JTAG controllers, and watchdog timers. Power management functions, thermal management functions, and digital control functions are collectively referred to as hardware management functions.
Many electronic systems utilize “point of load” (POL) converters. These are mainly small, integrated DC-to-DC down converters. POL converters have an enable pin to turn power on. Power distribution is typically implemented at higher voltages and then converted to lower voltages near low-voltage components to avoid I*R losses. In some cases (e.g., in some battery-powered systems), voltage can also be increased as necessary. Some applications use the same voltage rails to more than one chip. Under such conditions, only one instance of the DC-to-DC converter is typically used, and MOSFETs are then used to feed the same rail to all devices and meet their sequencing requirements. Other applications may use a linear regulator in place of either the MOSFET or POL converter.
Larger system boards can have many power supply domains and many POL converters. Parts on the board can have varying requirements for which power supplies need to be powered up or down in particular orders. Also monitoring is important for reliable reset generation. Moreover, the need for dynamic power management is becoming popular to control the heat dissipated by a given device. As an example, processor speed may be reduced if temperature gets too high or if the processor is drawing too much current. More popularly, processor speed is increased when needed, but that requires voltage changes before clock changes which must be monitored; otherwise, failures occur. Lower power is accomplished by reducing the clock speed (which is proportional to power) and reducing power supply voltage. It is also true that, if more performance is desired and temperature is acceptable, power supply voltage can be increased and clock speed increased. Clock changes are determined by the monitored temperature and system needs. Power supply voltage and current (power) is monitored as well to ensure that the system is operating within design margins. This includes modifying monitoring limits if the power supply voltage is adjusted in the system. Board power supply systems typically monitor voltage, current, and temperature. Finally, capturing conditions when a fault occurs, known as fault logging, is becoming a critical requirement of systems. Logging the voltage, current, and temperature conditions if a fault or an out-of-spec condition is detected is becoming commonplace and is frequently essential to system debug.
As a result, both simple boards (e.g., having fewer power supplies) and complex boards (e.g., having more power supplies) may require tightly integrated thermal and control paths, power supply monitoring, sequencing, and general control. Standard off-the-shelf power management IC's require that enable pins be partitioned across multiple devices if one device does not have the resources to perform the complete power management function of the board. This further complicates power management designs. In many cases, pin limitations force design tradeoffs that reduce board reliability. Another conventional approach is to design a different specific solution for each different system, but that can be both costly and time consuming. Another approach is to design a single integrated component that can handle all or at least most applications. Such an approach is wasteful and inefficient for relatively simple applications.